Purification of glyceride oils



Nov. 6, 1956 B. CLAYTON PURIFICATION OF GLYCERIDE OILS Filed May 1, 1951 HEAT/N6 HEAT/N0 AMMONIA VAPOR/ZINE l/YDR OXIDE AMMON/ UM fiMMON/fl ABSOEPTI ON INVENTOR.

g'amin Chylon United States Patent PURIFICATION OF GLYCERIDE OILS Benjamin Clayton, Houston, Tex.

Application May 1, 1951, Serial No. 223,956

6 Claims. (Cl. 260-425) This invention relates to the purification of glyceride oils, and more particularly, to a process in which a crude glyceride oil containing gums and free fatty acids is first treated with aqueous ammonia as a refining agent in order to enable the separation of gums and at least a portion of the free fatty acids from the oil, the process having as its primary advantage the reduction in loss of neutral glyceride oil and the recovery of high quality gums having a low glyceride oil content.

In the refining of edible glyceride oils, the conventional refining reagent is either an aqueous solution of caustic soda or an aqueous solution of soda ash. Such refining reagents precipitate the gums and neutralize free fatty acids to form sodium soaps and enable an aqueous phase known as soapstock to be separated from the oil. Where soda ash is employed as the refining reagent the separated oil is ordinarily rerefined with a small quantity of an aqueous solution of caustic soda. In either case the soapstock initially separated from the oil contains substantially all of the gums admixed with alkali metal soaps and while the oil content of such soapstock is very low when the refining is carried out in a modern continuous process, the caustic-produced gums are degraded and as a practical matter, it is impossible to recover high quality gums from either soapstock.

The gums are valuable materials and considerable amounts of crude glyceride oils, particularly corn oils and soyabean oils, are degummed in order to recover undecomposed gums prior to alkali refining. In commercial de gummin g operations, water in amounts ranging between 1 and 5% is initially mixed with the oil to precipitate the gums and the resulting mixture continuously centrifugally separated into an aqueous phase containing the gums and an oil phase. The separated gums will, however, ordinarily contain between 35 and 45% free oil and this free oil represents an important economical loss since the oil is more valuable than the gums themselves.

In the process of the present invention I have found that the employment of aqueous ammonia, i. e., an aqueous solution of ammonium hydroxide, as the degumming or partial refining reagent enables gums containing a much smaller percentage of oil to be separated from the oil. This results in a reduced loss of glyceride oils and furthermore, high quality gums may be recovered from the separated material.

In general, a substantial quantity or" any free fatty acids present in the oil are also neutralized and separated with the gums in the form of ammonium soaps. When refining low free fatty acid oils, a sufficient amount of the ammonium hydroxide refining reagent may, if desired, be employed to neutralize substantially all of the free fatty acids, although when refining high free fatty acid oils it is preferable to employ insuiiicient ammonium hydroxide to neutralize all of the free fatty acids. In any case, in carrying out the improved process of the present invention, an aqueous phase containing the gums and a much smaller amount of glyceride oil than is possible in the prior degumming operations discussed above is separated from the oil and this aqueous phase may be treated to remove ammonia therefrom so as to produce gums containing a reduced amount of glyceride oil. As stated above, a substantial saving of neutral glyeeride oil over conventional degumming operations results and it becomes possible to recover high quality gums without excessive loss of glyceride oil. The oil after the gums have been separated therefrom may be treated, if desired, to recover small amounts of residual ammonia left therein and is ordinarily rerefined with an aqueous solution of caustic soda. The loss of glyceride oil in such a rerefining process is, in general, almost negligible.

It is therefore an object of the present invention to provide an improved process of recovering gums from crude glyceride oils while minimizing the amount of neutral oil lost in the process.

Another object of the invention is to provide a process in which aqueous ammonia is first employed as a refining reagent in order to separate and recover high quality gums while at the same time reducing the amount of neutral oil lost in the process.

Other objects and advantages of the invention will appear in the following description thereof which is given in connection with the attached drawing, which is a schematic diagram of apparatus suitable for carrying out the present invention.

Referring more particularly to the drawings, oil may be delivered from a source of supply shown as the tank 10 to a heating device 11 by means of a pump 12. The heating device 11 may include a coil 13 through which oil is pumped surrounded by a casing 14 through which any suitable heating medium may be passed. Aqueous ammonia may be withdrawn from the supply tank 16 by means of a pump 17 and pumped through a heating device 18 which may be similar to the heating device 11. The oil from the heating device 11 may be delivered to the mixer 19 which may be any suitable type of flow mixer and the ammonium hydroxide from the heating device 18 may likewise be delivered to the mixer '19. The oil may be forced through the mixer 19 by the pumps 12 and 17 and passed through another heating device 21 and then through a cooling device 22 and delivered into a continuous centrifugal separator 23.

In the centrifugal separator 23 the mixture is separated into a lighter oil eilluent which is delivered from the separator through a spout 24 and a heavier aqueous efiluent which may be delivered from the separator through a spout 26. The oil eflluent delivered through the spout 24 is predominantly glyceride oil from which the gums and at least a portion of the free fatty acids have been removed and this oil effiuent will ordinarily contain a very small amount of water which in turn contains a small amount of ammonia as ammonium hydroxide. If the oil is to be immediately rerefined or washed, it is ordinarily not economical to attempt to recover the small amount of ammonia present in the oil eflluent. If desired, however, the oil eilluent may be delivered directly to an ammonia stripping operation through the pipe 27. That is to say, the oil efiiuent may be delivered into a steam stripping tank 28 and steam may be passed upwardly through a body of oil in the tank 28 by means of a steam distributor 29. The level of the oil in the tank 28 may be maintained by a float shown diagrammatically at 31 which float actuates a float valve 32 in a discharge pipe 33 for the tank 28.

The pipe 33 may deliver oil from the tank 28 into a vacuum stripping tank 34 and a vacuum may be maintained in the tank 34 by means of a steam vacuum pump 36 of any known or suitable type into which steam is delivered by means of a pipe 37. Discharge from the vacuum pump 36 may supply steam to the steam distributor 29 in the tank 28. A desired level may be maintained in the vacuum stripping tank 34 by means of a float shown diagrammatically at 38 controlling a float valve 39 in a discharge pipe 41 for the vacuum stripping tank 34. Most of the ammonia can be stripped from the oil in the steam stripping tank 28 and delivered as mixed vapors of steam and ammonia through a pipe 42 to an ammonia absorbing system shown at 43. Any remaining ammonia in the oil may be stripped therefrom in the vacuum stripping tank 34 and delivered into the steam stripping tank 28 and also discharged as vapor through the pipe 42.

The heavier elfiuent discharged from the centrifugal separator 23 through the spout 26 contains substantially all of the ammonia originally introduced into the system in the form of ammoniated gums, ammonia soaps and any excess aqueous ammonia used and will usually be approximately 50% water by weight. It has been found that the ammonia may be recovered from such heavier efliuent to leave an aqueous phase of gums and fatty acids more expeditiously if the separated aqueous phase is first diluted by at least its weight of water. This water may be pumped from the tank 44 by means of a pump 46 and delivered into a flow mixer 47 into which the aqueous efiiuent from the separator 23 is also delivered. Preferably, the pumps 12, 17 and 46 form part of a suitable proportioning system; for example, the pumps may all be driven from a variable speed motor 48 and the proportioning system may have speed change devices 49 and 51 so that the various pumps may be driven at adjustable speeds in order to control the proportions of oil, aqueous ammonia and water delivered by the pumps to the process.

The diluted aqueous phase from the mixer 47 may be delivered into an ammonia vaporizing tank 52 forming part of an ammonia vaporizing system. The tank 52 may contain a heating coil 53 positioned below the liquid level in the tank 52, such liquid level being maintained by a float 54 actuating a float valve 56 in a discharge pipe 57 for the tank 52. The upper portion of the tank 52 may be connected to the pipe 42 leading to the ammonia absorbing system 43 and ordinarily, the aqueous phase in the tank 52 will be heated to the boiling point of the aqueous phase at the pressure maintained in the tank 52 and the ammonia absorbing system 43. This pressure will ordinarily be somewhat below atmospheric pressure and sufficient heat will ordinarily be supplied by means of the heating coil 53 to boil oil the major portion of the diluting water added in the mixer 47. The ammonia soaps are largely decomposed in the tank 52 and most of the ammonia contained in the diluted aqueous effluent is vaporized and delivered to the ammonia absorbing system 43 along with substantial quantities of water vapor.

The material discharged from the vaporizing tank 52 through the pipe 57 will ordinarily contain a small amount of ammonia and this ammonia may be removed in a steam stripping tank 58 which may be similar to the steam stripping tank 28 and in a vacuum stripping tank 59 which may be similar to the vacuum stripping tank 34. An aqueous emulsion of gums and fatty acids is thereby discharged from the system through a pipe 61 connected to the lower portion of the vacuum stripping tank 59. While the ammonia recovery systems illustrated are effective to remove substantially all of the ammonia from the oil effluent and from the aqueous gum effluent, any other suitable ammonia recovery steps may be employed.

The ammonia absorption system 43 may include a closed tank 62 into which the ammonia and water vapors from the tanks 28, 52 and 58 are delivered. Water is initially added to the tank 62 and thereafter an ammonium hydroxide solution may be withdrawn from the lower portion of the tank 62 by means of a pump 63 and passed through a cooling device 64 and then recirculated into the upper portion of the tank 43 through a distributor 66. Water vapors delivered into the tank 62 are thereby condensed and ammonia is dissolved in the condensed water in the system. By regulating the temperature obtained in the cooling device 64 and thus the temperature of the water or ammonia solution delivered into the tank 62, a desired pressure, usually somewhat below atmospheric, may be maintained in the ammonia absorbing system 43 and in the tanks 28, 52 and 58. By varying the length of time that the aqueous ammonia is recirculated in the ammonia absorption system 43 an aqueous ammonia having the desired concentration for re-use in the process may be obtained and an ammonium hydroxide solution may be returned to the supply tank 16 by means of a pump 66. That is to say, the strength of the aqueous ammonia may be regulated by the depth of liquid maintained in the tank 62, all other conditions in the process remaining constant, and this in turn may be controlled by a float 67 actuating a float valve 68 in the pipe 69 leading to the pump 66.

In carrying out the process of the present invention, the concentration of ammonium hydroxide employed may vary from approximately 1.5% to the concentration of commercial concentrated ammonium hydroxide, i. e., approximately 29%. The preferred range of concentration, however, is between approximately 3 and 10%. In this connection, it is preferred to maintain the concentration of aqueous ammonia below that at which substantial liberation of ammonia vapor will take place in the centrifugal separator 23 at the temperature and pressure maintained therein. The pressure at which separation takes place will ordinarily be atmospheric pressure and the temperature of separation will ordinarily range between and F.

In general, it is preferred to subject the mixture of crude oil and aqueous ammonia delivered from the mixer 19 to temperatures in the range of 180 to 200 F. This temperature may be obtained by preheating the oil and ammonium hydroxide in the heating devices 11 and 18 or by heating the resulting mixture in the heating device 21, or by supplying a portion of the heat prior to mixing and a portion subsequent to mixing. That is to say, the desired temperatures may be obtained either by preheating or by heating after mixing, or both.

As stated above, the desired temperature of separation is ordinarily between 140 and 150 F., and the mixture from the heater 21 may therefore be cooled in the cooling device 22 to the desired separation temperature. It has been found that the aqueous ef'i'luent from the centritugal separator 23 contains a reduced content of glyceride oil and that the oil efiluent contains less gum content if the mixture in the process is subjected to the higher temperatures of 180 to 200 F., and then rapidly cooled to a separation temperature between 140 and 150 F., although good results are obtained by omitting the cooling step, in which case the highest temperature reached in the process will ordinarily be between 140 and F., and preferably between 150 and 175 F.

The amount of reagent employed will ordinarily range between 1% and 3.5% by weight of the oil and the amount of water added in the mixer 47 will ordinarily range between 1 and 3 times the weight of the aqueous effluent discharged through the spout 26.

As an example, a crude soybean oil containing gums and having a free fatty acid content of 0.5% by weight was treated with 1.5% of a 3.6% ammonium hydroxide solution. The oil was preheated to 150 F. and the resulting mixture then heated to 175 F. This mixture was centrifugally separated at the latter temperature and the aqueous efiluent was a dark liquid material which flowed readily and contained 16.7% glyceride oil on a dry basis. Another portion of the same oil was treated with 1% of a 7.3% ammonium hydroxide solution under the same conditions and the aqueous efiiuent contained 14.5% glyceride oil on a dry basis. By heating the mixture to a somewhat higher temperature and then cooling and separating at a temperature between 140 and 150 F., it is possible to still further reduce the glyceride oil content of the aqueous efiiuent from the separator, and furthermore, the oil effluent is cleaner in that it contains a substantially lesser amount of dissolved gums and ammonium soap.

The oil recovered from the present process is a high quality semi-refined oil and is ordinarily subjected to a refining step employing caustic soda as the refining reagent. The losses in the partial refining step of the present invention are much lower than those produced in conventional degumming operations in which the aqueous phase will ordinarily contain between 35 and 45% glyceride oil on a dry basis. The oil loss in the rerefining step is very low and a high quality neutral oil is produced in the rerefining step.

The gums recovered from the present invention are high quality undecomposed phosphatidic materials containing a reduced amount of glyceride oil. Such gums may be dried to form a product similar to commercial vegetable oil phosphatides and are useful for the same purposes and are particularly suitable for employment in a gum splitting operation without an intermediate deoiling operation.

This application is a continuation-in-part of my copending application Serial No. 184,891, filed September 14, 1950, now Patent No. 2,686,794.

I claim:

1. The process of purification of crude glyceride oils containing gums and free fatty acids, which comprises, admixing with said oil an amount of aqueous ammonia ranging between 1 and 3.5% by weight of the oil and having a concentration between 1.5 and 29%, continuously centrifugally separating the resulting mixture at a temperature between 140 and 175 F. into an aqueous etfiuent containing gums having a reduced content of glyceride oil and an oil eifiuent substantially free from gums, diluting said aqueous efiluent with an amount of water ranging from 1 to 3 times the weight of said aque ous effluent, and vaporizing water and ammonia from the diluted efiluent to provide a product substantially free of ammonia.

2. The process of purification of crude glyceride oils containing gums and free fatty acids, which comprises, admixing with said oil an amount of aqueous ammonia ranging between 1 and 3.5% by weight of the oil and having a concentration between 1.5 and 29%, supplying sufficient heat to the materials in said process to raise the temperature of the resulting mixture to between 180 and 200 F., thereafter rapidly cooling said mixture to a temperature between 140 and 150 F. and continuously centrifugally separating said mixture at the last-mentioned temperature into an aqueous efiluent containing gums having a reduced content of glyceride oil and an oil efliuent substantially free from gums.

3. The process of purification of crude glyceride oils containing gums and free fatty acids, which comprises, admixing with said oil an amount of aqueous ammonia ranging between 1 and 3.5% by weight of the oil and having a concentration between 3 and 10%, supplying sufficient heat to the materials in said process to raise the temperature of the resulting mixture to between 180 and 200 F., thereafter rapidly cooling said mixture to a temperature between and F. and continuously centrifugally separating said mixture at the last-mentioned temperature into an aqueous effluent containing gums having a reduced content of glyceride oil and an oil effluent substantially free from gums.

4. The process of purification of crude glyceride oils containing gums and free fatty acids, which comprises, admixing with said oil an amount of aqueous ammonia ranging between 1 and 3.5% by weight of the oil and having a concentration between 3 and 10%, supplying sufiicient heat to the materials in said process to raise the temperature of the resulting mixture to between and 200 F., thereafter rapidly cooling said mixture to a temperature between 140 and 150" F., continuously centrifugally separating said mixture at the last-mentioned temperature into an aqueous efiiuent containing gums having a reduced content of glyceride oil and an oil effluent substantially free from gums, diluting said aqueous efiiuent with an amount of water ranging from 1 to 3 times the weight of said aqueous efliuent, and vaporizing water and ammonia from the diluted efiiuent to provide a product substantially free of ammonia.

5. The process of purification of crude glyceride oils containing gums and free fatty acids, which comprises, admixing with the oil an amount of aqueous ammonia sufficient to precipitate said gums and react with at least a part of said free fatty acids, supplying suflicient heat to the materials in said process to produce a mixture of a temperature between about 180 F. and about 200 F., thereafter rapidly cooling said mixture to a temperature between about 140 F. and about 150 F., and separating the mixture at substantially the last mentioned temperature into an aqueous gum-containing efliuent and an oil efiiuent.

6. The process of purification of crude glyceride oils containing gums and free fatty acids, which comprises, admixing with the oil an amount of aqueous ammonia sufficient to precipitate said gums and react with at least a part of said free fatty acids, separating the resulting mixture into an aqueous gum-containing effinent and an oil effluent, diluting said aqueous gum-containing effluent with at least its weight in water, and vaporizing water and ammonia from the diluted efliuent to produce a product substantially free of ammonia.

References Cited in the file of this patent UNITED STATES PATENTS 1,900,132 Rosenstein Mar. 7, 1933 2,462,923 Thurman Mar. 1, 1949 2,686,794 Clayton Aug. 17, 1954 FOREIGN PATENTS 226,767 Great Britain 1925 

1. THE PROCESS OF PURIFICATION OF CRUDE GLYCERIDE OILS CONTAINING GUMS AND FREE FATTY ACIDS, WHICH COMPRISES, ADMIXING WITH SAID OIL AN AMOUNT OF AQUEOUS AMMONIA RANGING BETWEEN 1 AND 3.5% BY WEIGHT OF THE OIL AND HAVING A CONCENTRATION BETWEEN 1.5 AND 29%, CONTINUOUSLY CENTRIFUGALLY SEPARATING THE RESULTING MIXTURE AT A TEMPERATURE BETWEEN 140 AND 175* F. INTO AN AQUEOUS EFFLUENT CONTAINING GUMS HAVING A REDUCED CONTENT OF GLYCERIDE OIL AND AN OIL EFFLUENT SUBSTANTIALLY FREE FROM GUMS, DILUTING SAID AQUEOUS EFFLUENT WITH AN AMOUNT OF WATER RANGING FROM 1 TO 3 TIMES THE WEIGHT OF SAID AQUEOUS EFFLUENT, AND VAPORIZING WATER AND AMMONIA FROM THE DILUTED EFFLUENT TO PROVIDE A PRODUCT SUBSTANTIALLY FREE OF AMMONIA. 